1. Field of the Invention
The present general inventive concept relates to a two-way paper pickup system and a printer adopting the same, and more particularly, to a two-way paper pickup system in which both a feed tray and a paper cassette are available, and a printer adopting the same.
2. Description of the Related Art
In general, since most inkjet printers are manufactured as low-cost popular types, only a paper tray is adopted as a paper feed mechanism to minimize manufacture costs. FIGS. 1 and 2 illustrate a conventional inkjet printer and a conventional paper feed mechanism adopted by the conventional inkjet printer, respectively. Referring to FIG. 2, the conventional paper feed mechanism includes a feed tray 110 in which paper S is placed, a pickup roller 121 that moves the paper S placed on the feed tray 110, a pickup roller supporter 123 that delivers a driving force to the pickup roller 121 and pressurizes the pickup roller 121 onto the paper S, a resistance plate 140 that allows sheets of the paper S transferred by the pickup roller 121 to be supplied to a feed roller 130 one by one; and the feed roller 130 that supplies the paper S to a printing unit (not shown).
A process of supplying the paper S using the conventional paper feed mechanism will now be described with reference to FIGS. 1 and 2. First, the pickup roller supporter 123 and the pickup roller 121, fixed by an end of the pickup roller supporter 123, press the paper S on the feed tray 110 with their own weight. In this case, when the pickup roller supporter 123 delivers a driving force to the pickup roller 121, the delivered driving force rotates the pickup roller 121 to transfer the paper S toward the resistance plate 140. A plurality of projections 145 are formed on the resistance plate 140 to separately supply the paper S to the feed roller 130. When the paper S is stopped by the projections 145, only a sheet of the paper S directly contacting the pickup roller 121 is transferred to the feed roller 130. This method is referred to as a paper separation method using a resistance plate.
There is a growing need to develop popular-type printers adopting a paper feed mechanism, such as that shown in FIG. 2, that can use both nonstandard sized paper of various types and sizes and standard sized paper, e.g., A4, B5, or letter sized paper. Accordingly, in a tray-type feed mechanism adopted by a conventional inkjet printer, a paper pickup system that picks up and supplies sheets of paper S one by one has the pickup roller 121 installed at one side of the feed tray 110 as shown in FIG. 3B. That is, as shown in FIGS. 3A and 3B, which are a plan view of and a rear view of the paper pickup system, respectively, the pickup roller 121 is installed at one side of the feed tray 110 rather than at a center thereof, and a paper guide 115 is installed at the opposite side of the feed tray 110 so that the paper S does not sway from one side to another. In particular, the paper guide 115 is installed such that the paper guide 115 can slide on the feed tray 110 along the width direction. Therefore, the location of the paper guide 115 can be adjusted to a size of the paper S.
A reason for locating the pickup roller 121 to one side of the feed tray 110 is to allow paper having various sizes to be transferred toward the resistance plate 140. If the pickup roller 121 is installed at a center of the feed tray 110, it is impossible to move very small sized paper. In general, a minimum width of paper that can be fed in an inkjet printer is about 3 inch.
However, in a case where paper with various types or sizes are fed by only one feed tray, such as the feed tray 110, the performance of feeding paper is lower than when using a feed cassette dedicated to specific sized paper, e.g., A4 sized paper. Further, it is more difficult to feed special type paper, such as overhead transparency paper (OHP), label paper, and photo paper, only using one feed tray. In particular, the performance of feeding paper deteriorates when using low-quality paper to which a large amount of paper powder (paper dust) adheres. In this case, the pickup roller 121 becomes stained with the paper powder, thus considerably lowering the performance of feeding paper.